Wireless communication with interference mitigation

ABSTRACT

In one implementation, a wireless communications terminal includes a multi-element antenna. In addition, the terminal includes preliminary signal combiners to combine received signals output by corresponding pairs of antenna elements. For each preliminary signal combiner, the signal output by a first of the pair of elements provides a model of interference present in the received signal output by the second of the pair of elements. The preliminary signal combiner is configured to combine the signal output by the first element with the signal output by the second element to produce an initial interference-mitigated signal. The terminal also includes phase shifters to apply complex weights to interference-mitigated signals to produce complex-weighted versions of the interference-mitigated signals and effectively steer a main beam of the antenna to facilitate reception of a desired signal and another signal combiner to combine the complex-weighted versions of the interference-mitigated signals to produce an interference-mitigated output signal.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 17/138,990 filed on Dec. 31, 2020, the disclosures of which isincorporated herein by reference in their entirety.

TECHNICAL FIELD

The disclosure relates generally to wireless communication, and morespecifically to wireless communication with interference mitigation.

SUMMARY

According to one implementation of the disclosure, a wirelesscommunications terminal includes a multi-element antenna. In addition,the terminal includes preliminary signal combiners to combine receivedsignals output by corresponding pairs of antenna elements. For eachpreliminary signal combiner, the signal output by a first of the pair ofelements provides a model of interference present in the received signaloutput by the second of the pair of elements. The preliminary signalcombiner is configured to combine the signal output by the first elementwith the signal output by the second element to produce an initialinterference-mitigated signal. The terminal also includes phase shiftersto apply complex weights to interference-mitigated signals to producecomplex-weighted versions of the interference-mitigated signals andeffectively steer a main beam of the antenna to facilitate reception ofa desired signal and another signal combiner to combine thecomplex-weighted versions of the interference-mitigated signals toproduce an interference-mitigated output signal.

According to another implementation of the disclosure, a wirelesscommunications terminal includes an antenna array having a plurality ofm antenna elements arranged linearly and displaced from one another suchthat the displacement between each pair of adjacent antenna elementswithin the antenna array is substantially equal. “m” is a number thatreflects the number of antenna elements. In addition, the wirelesscommunications terminal includes a first plurality of m-1 phaseshifters. Each such phase shifter of the first plurality is coupled to aunique one of the antenna elements and is configured to receive, fromthe antenna element to which it is coupled, a signal received by theantenna element and to apply a complex weight to it to generate acomplex-weighted version of the signal received by the antenna element.The wireless communications terminal also includes a plurality of m-1first-stage signal combiners. Each such first-stage signal combinercorresponds to a unique one of the pairs of adjacent antenna elementswithin the antenna array and is coupled to a first one of the pair ofadjacent antenna elements and a phase shifter from the first pluralityof phase shifters that is coupled to the second of the pair of adjacentantenna elements. In addition, each such first-stage signal combiner isconfigured to receive, from the first of the pair of adjacent antennaelements, a signal received by the first antenna element, to receive,from the phase shifter coupled to the second of the pair of adjacentantenna elements, the complex-weighted version of the signal received bythe second antenna element, and to combine the signal received by thefirst antenna element and the complex-weighted version of the signalreceived by the second antenna element to generate an output signal. Thewireless communications terminal further includes a second plurality ofm-1 phase shifters. Each such phase shifter of the second plurality iscoupled to a unique one of the first-stage signal combiners and isconfigured to receive, from the first-stage signal combiner to which itis coupled, the output signal output by the first-stage signal combinerand to apply a complex weight to it to generate a complex-weightedversion of the output signal. The wireless communications terminal alsoincludes a second-stage signal combiner that is coupled to each of thephase shifters of the second plurality and that is configured to combinethe complex-weighted versions of the output signals output by the phaseshifters of the second plurality to generate an interference-mitigatedoutput signal for the antenna array. In addition, the wirelesscommunications terminal includes a first controller to set the complexweights applied by the first plurality of phase shifters to the signalsreceived by the antenna elements to which they are connected. Thisgenerates complex-weighted versions of the signals received by theantenna elements to which they are connected. This models interferencefrom a co-located wireless communication terminal. The terminal alsoincludes a second controller to set the complex weights applied by thesecond plurality of phase shifters to steer a main beam of the antennaarray to facilitate reception of a desired signal.

According to yet another implementation of the disclosure, signals arereceived with an antenna array that has a plurality of m antennaelements that are arranged linearly and displaced from one another suchthat the displacement between each pair of adjacent antenna elementswithin the antenna array is substantially equal. In addition, a firstset of complex weights to be applied to the signals received by m-1 ofthe antenna elements is accessed and applied to the signals received bythe m-1 antenna elements to generate complex-weighted versions of thecorresponding signals received by the m-1 antenna elements. For eachpair of adjacent antenna elements within the antenna array, the signalreceived by a first one of the pair of adjacent antenna elements iscombined with the complex-weighted version of the signal received by thesecond one of the pair of adjacent antenna elements to generate m-1output signals. A second set of complex weights to apply to the outputsignals also is accessed and applied to the output signals to generatecomplex-weighted versions of the output signals. The complex-weightedversions of the output signals then are combined to generate aninterference-mitigated output signal.

Other features of the present disclosure will be apparent in view of thefollowing detailed description of the disclosure and the accompanyingdrawings. Implementations described herein, including theabove-described implementations, may include a method or process, asystem, or computer-readable program code embodied on computer-readablemedia.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referencenow is made to the following description taken in connection with theaccompanying drawings.

FIG. 1 is a high level block diagram of a system for wirelesscommunication with interference mitigation in accordance with anon-limiting implementation of the present disclosure.

FIG. 2 is a flow chart of a method for wireless communication withinterference mitigation in accordance with a non-limiting implementationof the present disclosure.

FIG. 3 is a block diagram of a system for wireless communicationconfigured to provide interference mitigation.

FIG. 4 is a block diagram of a system for wireless communicationconfigured to provide interference mitigation.

DETAILED DESCRIPTION

Satellite communication systems may enable wireless voice and datacommunications around the world. In some cases, satellite communicationsystems enable communication in regions where other wirelesscommunication systems may not be available. For example, some wirelesscommunication systems may require terrestrial infrastructure (e.g., acell tower, a base station, etc.). It may not be possible to communicateusing these systems in regions where the necessary terrestrialinfrastructure does not exist or cannot be accessed. However, satellitecommunication systems still may be capable of communicating in suchregions. Examples of these regions include the oceans, the airways, thepolar regions, and developing and/or underdeveloped nations. Frequently,multiple satellite communication systems may be co-located (e.g., withina fixed relative area). For example, a ship equipped with two or moresatellite communication systems may have only a small deck area suitablefor installing the antennae for the satellite communication systems and,consequently, the antennae for the satellite communication systems maybe forced to be installed in close physical proximity to one another(e.g., within a few feet or yards of one another on the deck).Similarly, an aircraft equipped with two or more satellite communicationsystems may have limited external area suitable for mounting theantennae for the satellite communications systems. As a result, theantennae for the satellite communication systems may be mounted in closephysical proximity to one another.

In some cases, two or more co-located satellite communication systemsmay use similar, adjacent, neighboring, and/or overlapping frequencies(e.g., for transmit and/or receive functions of satellitecommunication). As a result, an output signal transmitted by a firstsatellite communication system may interfere with the ability of asecond, co-located satellite communication system to receive an inputsignal, and vice versa, particularly if the power of the output signalis significantly greater than the power of the input signal. Forexample, if the first satellite communication system transmits arelatively high-power output signal in a frequency band that isimmediately adjacent to the frequency band in which the second satellitecommunication system receives a relatively low-power input signal,components of the relatively high-power output signal may spill overinto the frequency band in which the second satellite communicationsystem receives the low-power input signal and, particularly due to thepower difference between the two signals, cause interference with therelatively low-power input signal, thereby degrading the performance ofthe second satellite communication system. Additionally oralternatively, the presence of the relatively high-power output signalmay cause reciprocal mixing in the receiver of the second satellitecommunication system also resulting in degradation of the secondsatellite communication system's ability to receive the relativelylow-power input signal. Local oscillators with relatively goodphase-noise performance may be employed to mitigate the effect of suchreciprocal mixing, but such high performance oscillators may berelatively expensive. Application of the interference mitigationtechniques described herein may enable the use of potentially cheaperlocal oscillators with worse phase-noise performance while stillproviding protection against reciprocal mixing.

In one specific example, an IRIDIUM® satellite terminal that uses L bandfrequencies between 616 and 1626.5 megahertz (“MHz”) to communicate withIRIDIUM® satellites may be co-located (e.g., on a ship or aircraft) withan INMARSAT® satellite terminal that uses L band frequencies between1525 and 1646.5 MHz to communicate with one or more INMARSAT®satellites. Consequently, transmissions to/from the INMARSAT® satelliteterminal may pose the potential for interference with transmissionsto/from the IRIDIUM® satellite terminal and vice versa. For example, theINMARSAT® satellite terminal may transmit communications in a frequencyband that is adjacent to a frequency band in which the IRIDIUM®satellite terminal receives transmissions from IRIDIUM® satellites.Accordingly, outbound transmissions from the INMARSAT® satelliteterminal may pose the potential to interfere with transmissions receivedby the IRIDIUM® satellite terminal and/or cause reciprocal mixing in theIRIDIUM® satellite terminal resulting in signal degradation,particularly given the relatively high power of output transmissionsfrom the INMARSAT® satellite terminal required to reach an INMARSAT®satellite and the relatively low power of transmissions received by theIRIDIUM® satellite terminal from an IRIDIUM® satellite. For example, thepower ratio of transmissions output by the INMARSAT® satellite terminalto transmissions received by the IRIDIUM® satellite terminal may be onthe order of +100 dB or more.

A satellite communication terminal may be configured to mitigate theeffects of interference from one or more other satellite communicationterminals in the event that the satellite communication terminal isco-located with one or more other satellite communications terminals,for example that use similar, adjacent, neighboring, and/or overlappingfrequencies. For instance, a satellite communication terminal configuredto receive a signal from one or more satellites even when co-locatedwith another satellite communication terminal that transmits an outputsignal in a similar, adjacent, neighboring, and/or overlapping frequencyband may employ beam steering (e.g., using complex weights, phaseshifters, etc.) to steer the main beam of the satellite communicationterminal's antenna toward the signal to be received (and, in some cases)away from the interfering signal output by the co-located satellitecommunication terminal. However, in some cases (e.g., if the power ofthe interfering signal is significantly greater than the power of thesignal to be received), such beam steering alone may not effectivelymitigate the interference caused by the signal transmitted by theco-located satellite communication terminal.

Additionally or alternatively, the satellite communication terminal mayemploy frequency domain filtering techniques (e.g., band pass filtering,for instance, using a surface acoustic wave (“SAW”) filter) to mitigateinterference caused by the signal transmitted by the co-locatedsatellite communication terminal. However, in some cases (e.g., if theinterfering signal is in a similar, adjacent, neighboring, and/oroverlapping frequency band and particularly if the power of theinterfering signal is significantly greater than the power of the signalto be received), such frequency domain filtering techniques alone maynot effectively mitigate the interference caused by the signaltransmitted by the co-located satellite communication terminal.

As described herein, implementations of the present disclosure mayprovide a satellite communication system configured to mitigate theeffects of interference from one or more other co-located satellitecommunication systems. For example, implementations of the presentdisclosure may utilize a combination of a main antenna or antenna arrayand an auxiliary antenna or antenna array to receive an interferingsignal from a co-located satellite communication system and subtract theinterfering signal from the signal received by the main antenna tomitigate the interference caused by the interfering signal to thedesired signal. In certain implementations, spatial filtering techniques(e.g., shaping an antenna's transmit/receive response) may be employedto mitigate interference caused by the co-located satellitecommunication system. For example, the primary antenna may be asteerable antenna (e.g., a switched beam antenna or an adaptive arrayantenna) configured to steer a beam (e.g., a main beam) of the primaryantenna in a direction perceived as advantageous for receiving thedesired satellite signal and the auxiliary antenna may be configured toreceive the interfering signal from the co-located satellitecommunication system such that the interfering signal received by theauxiliary antenna can be subtracted from the signal received by theprimary antenna to mitigate the effects of the interfering signalreceived by the primary antenna.

In certain implementations, the gain of such an auxiliary antenna may berelatively low compared to the gain of the primary antenna. Furthermore,complex weights may be applied to the signal received by such anauxiliary antenna to shift the amplitude and/or phase of the signalreceived by the auxiliary antenna in an effort to optimize thecancellation of the interfering signal from the co-located satellitecommunication system.

Alternative implementations of the present disclosure may utilize amultielement antenna in which individual elements of the antenna arepaired, with a first element of each pair being configured to receive aninterfering signal from a co-located satellite communication system suchthat, when the signal received by the first element of the pair iscombined with the signal received with the signal received by the secondelement of the pair, it cancels or otherwise mitigates the presence ofthe interfering signal from the co-located satellite communicationsystem in the signal received by the second element of the pair. In someimplementations, complex weights may be applied to the interferingsignal received by the first antenna element of each pair prior tocombining the signal received by the first antenna element with thesignal received by the second element so as to reduce the interferingsignal as much as possible at each pair. The interference-mitigatedsignals generated by each pair of antenna elements also may be combined.In some implementations, complex weights may be applied to theinterference-mitigated signals before they are combined so as to steer amain beam of the antenna to facilitate reception of the desired signal.Additionally, in some implementations, this architecture can be extendedsuch that pairs of pairs are combined, for example, to mitigate theeffect of additional interfering signals and/or to mitigate the effectof distinct components of one or more interfering signals.

With reference to FIG. 1 , a high level block diagram of a system 100for wireless communication is illustrated in accordance with anon-limiting implementation of the present disclosure. System 100includes satellites 10 and 20, wireless communication terminal 30 forreceiving a signal from satellite 20, and interfering wirelesscommunication terminal 50 for transmitting a signal to satellite 10.Wireless communication terminal 30 includes a primary antenna array 32,an auxiliary antenna array 34, a modem 36, a power receiver 38, a BeamSteering Controller (“BSC”) 40, and an Interference Canceller Controller(“ICC”) 42. Primary array 32 has one or more antenna elements 43 a-c,each of which includes a corresponding transmit/receive module 44 a-c.Auxiliary array 34 has one or more antenna elements 45 a-c, each ofwhich includes a corresponding receive module 46 a-c. For example,primary antenna array 32 may have 12 antenna elements, and auxiliaryantenna array 34 may have 3 antenna elements. Primary array 34 maytransmit and/or receive signals to satellite 20.

Interfering wireless communication terminal 50 includes one or moreantenna elements 52. Antenna elements 52 communicate with satellite 10.When interfering wireless communication terminal 50 is transmitting tosatellite 10, antenna 52 may send a relatively high power transmissionsignal (particularly when compared to the power of the signal thatwireless communication terminal 30 receives from satellite 20) frominterfering wireless communication terminal 50 to satellite 10. Therelatively high power transmission signal sent by interfering wirelesscommunication terminal 50 may be in a similar, adjacent, neighboringand/or overlapping frequency band to a frequency band in which wirelesscommunication terminal 30 is configured to receive signals fromsatellite 20. Furthermore, wireless communication terminal 30 may belocated in close proximity (e.g., less than 5 feet, between 5 and 15feet, between 15-50 feet, etc.) to interfering wireless communicationterminal 50. Thus, the relatively high power transmission signal sent byinterfering wireless communication terminal 50 may interfere with theability of wireless communication terminal 30 to receive the relativelylow power signal from satellite 20.

The BSC 40 may be configured to steer a main beam of primary antennaarray 32 in a desired direction to facilitate the transmission ofsignals to and/or the reception of signals from satellite 20. Forexample, BSC 40 may control complex weights applied by transmit/receivemodules 44 a-44 c to signals transmitted/received by antenna elements 43a-43 c to steer a main beam of primary antenna array 32 in the desireddirection. However, even with a main beam of primary antenna array 32positioned to facilitate the reception of the signal from satellite 20,the signal transmitted by interfering wireless communication terminal 50still may interfere with the ability of wireless communication terminal30 to receive the signal from satellite 20. For example, even if a mainbeam of primary antenna array 32 is steered in the direction ofsatellite 20 (and/or away from interfering wireless communicationterminal 50), the signal transmitted by interfering wirelesscommunication terminal 50 still may be received in the side lobe(s) ofprimary antenna array 32.

Therefore, auxiliary antenna array 34 may be used to sample the signaltransmitted by interfering wireless communication terminal 50 so thatthe sampled interfering signal may be subtracted from the signalreceived by primary antenna array 32 to produce an interferencemitigated signal that thereafter is provided to modem 36. In certainimplementations, a main beam of auxiliary antenna array 34 may besteered in a particular direction to facilitate reception of theinterfering signal from interfering wireless communication terminal 50.In certain implementations, power receiver 38 may measure the power inthe interference mitigated signal, and ICC 42 may control complexweights applied by receive modules 46 a-46 c to the signals received byantenna elements 45 a-45 c in an effort to minimize the power in theinterference mitigated signal. Furthermore, in certain implementations,the above-described signal processing may be performed at radiofrequencies (“RF”) (e.g., before the received signal is converted to anintermediate frequency, baseband, etc.).

With reference to FIG. 2 , a flow chart 200 of a method for wirelesscommunication with interference mitigation is illustrated in accordancewith a non-limiting implementation of the present disclosure. The methodillustrated in flow chart 200 may be performed by the wirelesscommunication terminal 30 illustrated in FIG. 1 . At step 210, a mainbeam of a primary antenna array is steered to a desired direction. Forexample, a desired signal to be received may be transmitted by asatellite orbiting the earth, and a main beam of the primary antennaarray may be steered in a direction favorable for receiving the desiredsignal. In some implementations, a main beam of the antenna array may besteered in the desired direction by defining complex weights to beapplied to the signals received by the antenna elements of the primaryantenna array. At step 220, complex weights to be applied by theauxiliary antenna array are set based on the direction of the main beamof the primary antenna array. As described in greater detail below, insome implementations, the complex weights to be applied may becalculated substantially in real-time as the main beam of the primaryantenna is steered, while, in other implementations, the complex weightsto be applied may have been predetermined (e.g., during a calibrationprocess) for each of a number of different possible directions in whichthe main beam of the primary antenna may be steered.

At step 230, a main signal is received by the primary antenna array. Themain signal may include noise from a signal transmitted by anothernearby wireless communication terminal. For example, the signaltransmitted by the nearby wireless communication terminal may bereceived in one or more side lobes of the primary antenna array. In somecases, the power of the signal transmitted by the nearby wirelesscommunication terminal may be significantly greater than the power ofthe signal desired to be received (e.g. +100 dB).

In parallel with receiving the main signal, at step 240, a secondarysignal is received with the auxiliary antenna array. The secondarysignal received by the auxiliary antenna array may include the signaltransmitted by the nearby wireless communication terminal. As such, theauxiliary antenna array may be said to sample the signal transmitted bythe nearby wireless communication terminal. In some implementations, theindividual antenna elements of the auxiliary antenna array may receivevariants (e.g., time- and/or phase-shifted variants) of the secondsignal. At step 250, the antenna elements of the auxiliary antenna arrayapply the previously set complex weights to the variants of thesecondary signal they received, thereby generating shifted (e.g.phase-shifted) variants of the secondary signal. At step 260, theshifted variants of the secondary signal are combined into aninterfering signal (e.g., that models the signal transmitted by thenearby wireless communication terminal).

At step 270, the interfering signal is subtracted from the main signal.Subtracting the interfering signal from the main signal may result innoise (e.g., the signal transmitted by the nearby wireless communicationterminal) being canceled or reduced from the main signal to enablefurther processing of a desired signal included within the main signal.The resulting signal, therefore, may be referred to as an interferencemitigated signal.

In some implementations, the power in the interference mitigated signalmay be monitored, and the weights to be applied by the antenna elementsof the auxiliary antenna array may be calculated to minimize (or atleast reduce) the power in the interference mitigated signal. Forexample, in some particular implementations, a calibration process maybe performed upon installation of the device and/or at intervalsthereafter to determine appropriate complex weights to be applied by theantenna elements of the auxiliary antenna array to minimize (or at leastreduce) the power in the interference mitigated signal for each of adefined number of possible directions in which a main beam of theprimary antenna array may be steered. Additionally or alternatively, thepower in the interference signal may be measured continually and used asfeedback to continually adapt the complex weights applied by the antennaelements of the auxiliary antenna array substantially in real-time.

In some implementations, the desired signal may be transmitted bysatellites within a constellation of two or more satellites orbiting theearth. Therefore, the direction of a main beam of the primary antennaarray may be changed relatively frequently to account for changes in theposition of a particular satellite from which the desired signal isbeing received as the particular satellite orbits the earth. As the beamof the primary antenna array is steered in this manner, occasionally themain beam of the primary antenna array may be pointed substantially inthe direction of the signal being transmitted by the nearby wirelesscommunication terminal. When this occurs, the noise in the main signalcaused by the nearby wireless communication terminal may make itdifficult or impossible to extract the desired signal from the mainsignal. Therefore, when it is determined that pointing the main beam ofthe primary antenna array may subject the primary antenna array tosubstantial interference from a nearby wireless communication terminal,the main beam of the primary antenna array may be steered in a differentdirection that is favorable for receiving the desired signal fromanother one of the satellites in the satellite constellation.

With reference to FIG. 3 , a block diagram of a wireless communicationterminal 300 configured to provide interference mitigation isillustrated in accordance with a non-limiting implementation of thepresent disclosure. A primary transmit/receive antenna array 310includes a number of antenna elements 312(a)-(m). The antenna elements312(a)-(m) collectively are configured to transmit and/or receivesignals. The primary transmit/receive antenna array 310 may besteerable, for example, to enable one or more main beams of the primarytransmit/receive antenna array 310 to be steered in directions that arefavorable for transmitting and/or receiving signals. For example, ifwireless communication terminal 300 is configured to communicate withone or more satellites, the primary transmit/receive antenna array 310may be steerable to train a main beam of the primary transmit/receiveantenna array 310 in directions favorable for communicating with atarget satellite. In some implementations, the antenna elements312(a)-(m) may include phase shifters that enable one or more main beamsof the primary transmit/receive antenna array 310 to be steered.

In some situations, when operating in a receive mode to receive adesired signal, the primary transmit/receive antenna array 310 mayreceive interfering signals in its side lobe(s). For example, if thewireless communication terminal 300 is located in close physicalproximity to another wireless communication terminal (not shown) thattransmits signals in a similar, adjacent, neighboring, and/oroverlapping frequency band to the frequency band in which the wirelesscommunication terminal 300 receives signals, the wireless communicationterminal 300 may receive signals transmitted by the other wirelesscommunication terminal in its side lobe(s). Although the gain in theside lobe(s) may be low relative to the gain in the main beam, if thepower of the interfering signal is high relative to the power of thesignal desired to be received, the interfering signal received in theside lobe(s) may degrade and/or interfere with the reception of thedesired signal.

An auxiliary receive antenna array 320 includes a number of auxiliaryantenna elements 322(a)-(n). In certain implementations, the number ofprimary antenna elements 312(a)-(m) in the primary transmit/receivearray 310 may be greater (even significantly greater) than the number ofauxiliary antenna elements 322(a)-(n) in the auxiliary receive antennaarray 320. The number of antenna elements in each antenna array 310 and320 may vary depending on the implementation taking into account factorssuch as, for example, cost, gain required, device form factor, etc.

The primary antenna elements 312(a)-(m) in the primary transmit/receiveantenna array 310 each may include an antenna 314(a)-(m) and atransmit/receive module 316(a)-(m). Each transmit/receive module316(a)-(m) may include one or more band pass filters (e.g. for filteringout frequencies outside of the frequency band(s) in which the wirelesscommunication terminal 300 is intended to receive signals), a low noiseamplifier (e.g., for amplifying received signals), a transmit poweramplifier (e.g., for amplifying signals to be transmitted),radio-frequency switches (e.g., for switching between transmit andreceive modes) and/or a phase shifter. The primary antenna elements312(a)-(m) of the primary transmit/receive antenna array 310 areconfigured to receive variants of a main signal (e.g., time and/or phaseshifted variants of the main signal). The outputs of the primary antennaelements 312(a)-(m) are combined by a radio frequency (RF) combiner 330.Each of these components in the primary transmit/receive antenna array310 may operate at RF.

BSC 340 is configured to steer a main beam of the primarytransmit/receive antenna array 310 in desired directions. For example,BSC 340 may control phase shifters included in the transmit/receivemodules 316(a)-316(m) to steer a main beam of the primarytransmit/receive antenna array 310.

The auxiliary antenna elements 322(a)-(n) in the auxiliary receiveantenna array 320 each may include an antenna 324(a)-(n) and a receivemodule 326(a)-326(n). Each receive module 326(a)-(n) may include one ormore filters (e.g., for filtering out frequencies outside of thefrequency bands in which the wireless communication terminal 300 isintended to receive signals), a low noise amplifier (e.g., foramplifying received signals), and a complex weight module for applyingcomplex weights to received signals (e.g., to shift the amplitude and/orphase of the received signals). The auxiliary antenna elements326(a)-326(n) of the auxiliary receive antenna array 320 are configuredto receive variants of a secondary signal (e.g., time and/or phaseshifted variants of the secondary signal). The outputs of the auxiliaryantenna elements 326(a)-326(n) are combined by an RF combiner 350.Similar to the components of the primary transmit/receive antenna array310, each of these components of the auxiliary receive antenna array 320may also operate at RF.

In certain implementations, the auxiliary receive antenna array 320 maybe configured to sample an interfering signal. For example, theauxiliary receive antenna array 320 may be configured to sample aninterfering signal transmitted by another wireless communicationterminal located in close physical proximity to wireless communicationterminal 300 that also may be received in the side lobe(s) of theprimary transmit/receive antenna array 310. In such cases, the output ofRF combiner 350, represents a model of the interfering signal receivedin the side lobe(s) of the primary transmit/receive antenna array 310and can be subtracted from the main signal received by the primarytransmit/receive antenna array 310 by RF combiner 330 to cancel ormitigate interference in the signal received by the primarytransmit/receive antenna array 310. This subtraction may occur at RF.The signal output from RF combiner 330 may be transmitted to modem 355for further processing by the wireless communication terminal 300. Insome implementations, the signal output from RF combiner 330 may beconverted to an intermediate frequency (e.g., a frequency lower than RFfrequencies) before being transmitted to modem 355.

In certain implementations, ICC 360 controls the complex weights appliedto the variants of the secondary signal received by the receive modules326(a)-326(n) of the auxiliary receive antenna array 320, for example,to minimize (or mitigate) the interference in the signal output by RFcombiner 330. The ICC 360 may adjust the complex weights according to analgorithm. For example, power receiver 370 may measure the power in thesignal output by RF combiner 330, and the algorithm may be configured toadjust the complex weights applied by the receive modules 326(a)-326(n)to minimize the power measured in the signal output by RF combiner 330.In certain implementations, the power receiver may be implemented as atuned power meter. Additionally or alternatively, the power receiver mayinclude a power detector that measures power in the bandwidth of thewireless communication terminal 300 at one or more frequencies to whichthe power detector is tuned.

In certain implementations, BSC 340 may be configured to steer a mainbeam of primary transmit/receive antenna array 310 to a predeterminednumber of different positions, and corresponding sets of complex weightsto be applied by the receive modules 326(a)-326(n) may be determined foreach of the predetermined positions of the main beam of primarytransmit/receive antenna array 310. These complex weights may bedetermined during a calibration process for wireless communicationterminal 300. The calibration process may be conducted while aninterfering signal is known to be present. For example, while anotherwireless communication terminal located in close physical proximity towireless communication terminal 300 is transmitting, BSC 340 may steer amain beam of primary transmit/receive antenna array 310 to each of thepredetermined different positions, and, for each position of the mainbeam of the primary transmit/receive antenna array 310, appropriatecomplex weights to be applied by receive modules 326(a)-326(n) may bedetermined to minimize the power in the signal output by RF combiner330. These complex weights then may be stored by ICC 360 (e.g., in atable or similar data structure). Then, when wireless communicationterminal 300 is operating in the receive mode, the BSC 340 maycommunicate an indication of the current position of a main beam of theprimary transmit/receive antenna array 310 to ICC 360, and ICC 360 mayset the appropriate complex weights to be applied by the receive modules326(a)-(n) based on the current position of the main beam of the primarytransmit/receive antenna array 310 as determined during the calibrationprocess.

Additionally or alternatively, ICC 360 continually may update theweights to be applied by receive modules 326(a)-(n) in an effort tocontinually minimize the power in the signal output by RF combiner 330as measured by power receiver 370. In such implementations, BSC 340 maybe configured to steer a main beam of primary transmit/receive antennaarray 310 to a predetermined number of different positions or,alternatively, the different positions to which BSC 340 can steer themain beam of primary transmit/receive antenna array 310 may not bepredetermined. For example, BSC 340 may continually adjust the phaseshifts to be applied by transmit/receive modules 312(a)-312(m) to steerthe main beam of primary transmit/receive antenna array 310 to differentpositions perceived as favorable for transmitting a signal to and/orreceiving a signal from one or more desired targets (e.g., satellitesorbiting the earth).

In some implementations, wireless communications terminal 300 may beconfigured to receive a desired signal from two or more satellitesorbiting the earth. In such implementations, primary transmit/receiveantenna array 310 may be configured to produce multiple different mainbeams, each of which may be steered independently from the other(s). Forexample, primary transmit/receive antenna array 310 may be configured toproduce a handoff beam and a traffic beam. The handoff beam continuallymay be scanned to identify and locate one or more satellites with whichthe wireless communication terminal 300 can communicate at a given time.If multiple satellites are available for communication with the wirelesscommunication terminal 300, a preferred satellite for the wirelesscommunication terminal 300 to communicate with may be determined basedon, for example, signals received from the different satellites in thehandoff beam. Meanwhile, the traffic beam may handle actual traffic(e.g., voice or data) and, when multiple satellites are available forwireless communication terminal 300 to communicate with, may be steeredto positions perceived as being favorable for communicating with thepreferred satellite. In such implementations, modem 355 may have twoinput ports, one for signals received in the handoff beam and the otherfor signals received in the traffic beam.

Furthermore, in some implementations, auxiliary receive antenna array320 also may be configured to produce multiple different main beams thatcan be steered independently of each other, for example, a handoff beamand a traffic beam. In such implementations, the signal received in thehandoff beam of auxiliary antenna array 320 may be used to mitigateinterference in the signal received in the handoff beam of the primarytransmit/receive antenna array 310 and the signal received in thetraffic beam of auxiliary receive antenna array 320 may be used tomitigate interference in the signal received in the traffic beam of theprimary transmit/receive antenna array 310, for example, according tothe interference mitigation techniques described herein (e.g., bycoordinating the steering of the beams of the primary transmit/receiveantenna array 310 and the auxiliary receive antenna array 320.

In certain scenarios, steering a main beam of primary transmit/receiveantenna array 310 to track a particular satellite may result in steeringthe main beam of primary transmit/receive antenna array 310 in adirection that causes the interfering signal to be received in the mainbeam of primary transmit/receive antenna array 310. In such scenarios,the auxiliary receive antenna array 320 may not be effective inmitigating interference in the primary transmit/receive antenna array310. Thus, if wireless communication terminal 300 determines thatsteering a main beam of primary transmit/receive antenna array 310 totrack a particular satellite will result in the interfering signal beingreceived in the main beam of primary transmit/receive antenna array 310,wireless communication terminal 300 instead may steer the main beam ofprimary transmit/receive antenna array 310 to initiate communicationswith a different satellite.

In certain alternative implementations, the model of the interferingsignal may be subtracted from the main signal at an intermediatefrequency (e.g., a frequency that is lower than RF frequencies) insteadof at RF. For example, in such implementations, the transmit/receivemodules 316(a)-(m) may include circuitry (e.g., including a localoscillator) that converts the variants of the main signal received at RFto an intermediate frequency. After converting the variants of the mainsignal to the intermediate frequency, the transmit/receive modules316(a)-(m) also may filter (e.g., using a bandpass filter) and/oramplify (e.g., using a low noise amplifier) the received signals. Theintermediate frequency signals output by the transmit/receive modules316(a)-(m) then may be transmitted to combiner 330 where they arecombined at the intermediate frequency instead of at RF. Alternatively,in some implementations, the signals output by transmit/receive modules316(a)-(m) may be output at RF and combined into an RF main signal thatis converted to the intermediate frequency before being transmitted tocombiner 330. The receive modules 326(a)-326(n) of the auxiliary receiveantenna array 320 also may convert the variants of the secondary signalthat they receive from RF to the intermediate frequency before thesignals are combined by combiner 350. The resulting intermediatefrequency model of the interfering signal then may be subtracted fromthe intermediate frequency main signal by combiner 330. Alternatively,the variants of the secondary signal received by antenna elements324(a)-(n) may be combined at RF by combiner 350, and the combinedsignal then may be converted to the intermediate frequency before beingsubtracted from the main signal by combiner 330. In such alternativeimplementations, the complex weights applied to the variants of thesecondary signal by the receive modules 326(a)-(n) may be determined tominimize the power measured in the signal that results from subtractingthe intermediate frequency model of the interfering signal from theintermediate frequency main signal.

In still other alternative implementations, the variants of the mainsignal received by the primary antenna elements 312(a)-(m) may beconverted to digital baseband before being combined. Similarly, themodel of the interfering signal received in the side lobe(s) of theprimary transmit/receive antenna array 310 also may be converted todigital baseband before being subtracted from the main signal. Forexample, in such implementations, the signals output by transmit/receivemodules 316(a)-(m) (e.g., at RF or an intermediate frequency) may beconverted to digital baseband (e.g., by modems or demodulators) beforebeing combined into a digital baseband main signal. Alternatively, thesignals output by transmit/receive modules 316(a)-(m) may be combined togenerate a main signal (e.g., an RF or intermediate frequency mainsignal) that then is converted to a digital baseband main signal (e.g.,by a modem or a demodulator). Similarly, the signals output by receivemodules 326(a)-326(n) (e.g., at RF or an intermediate frequency) may beconverted to digital baseband (e.g., by modems or demodulators) beforebeing combined to generate a digital baseband model of the interferingsignal that then may be subtracted from the digital baseband mainsignal. Alternatively, the signals output by receive modules 326(a)-(n)may be combined by combiner 350 to generate a model of the interferingsignal that then is converted to digital baseband (e.g., by a modem ordemodulator) and subtracted from the digital baseband main signal. Insuch alternative implementations, the complex weights applied to thevariants of the secondary signal by the receive modules 326(a)-(n) maybe determined to minimize the power measured in the signal that resultsfrom subtracting the digital baseband model of the interfering signalfrom the digital baseband main signal.

With reference to FIG. 4 , a block diagram of a wireless communicationterminal 400 configured to provide interference mitigation isillustrated in accordance with a non-limiting implementation of thepresent disclosure. As illustrated in FIG. 4 ., wireless communicationterminal 400 includes a multielement antenna 402 having m antennaelements 404(1)-404(m). In some implementations, the antenna elements404(1)-404(m) may be arranged in a linear array. Additionally oralternatively, in some implementations the antenna elements404(1)-404(m) may be arranged such that the displacement between eachindividual antenna element is substantially equal.

The antenna elements 404(1)-(m) each may be configured to transmitand/or receive signals. In addition, the multielement antenna 402 may besteerable, for example, to enable one or more main beams of themultielement antenna 402 to be steered in directions that are favorablefor transmitting and/or receiving signals and/or to enable one or morenulls of the multielement antenna 402 to be steered in desirabledirections (e.g., in the direction of a source of interference). Forexample, if wireless communication terminal 400 is configured tocommunicate with one or more satellites while being collocated with apotential source of interference (e.g., another communications terminalthat uses similar, adjacent, neighboring, and/or overlapping frequencies(e.g., for transmit and/or receive functions of satellitecommunication)), the multielement antenna 402 may be steerable to traina main beam of the multielement antenna 402 in directions favorable forcommunicating with a target satellite while also steering a null in thedirection of the potential source of interference.

As illustrated in FIG. 4 , in some implementations, individual antennaelements 404(1)-404(m) may include transmit/receive modules406(1)-406(m). Such transmit/receive modules 406(1)-406(m) may includebandpass filters, low noise amplifiers, transmit power amplifiers, RFswitches (e.g., for switching from transmit to receive mode and viceversa), and/or other components configured to facilitate thetransmission and/or reception of signals. In addition, individualantenna elements 404 may be paired with adjacent antenna elements 404such that the outputs of the transmit/receive modules 406 of each suchpair of antenna elements are combined by one of a plurality of signalcombiners 408(1)-408(m-1). In this manner, one antenna element 404 ofeach such pair of antenna elements may be configured to receive aninterfering signal (e.g., from a collocated communications terminal orother interference source) such that the interfering signal, or a modelof the interfering signal, may be subtracted from the signal received bythe other antenna element 404 of the pair by the corresponding signalcombiner 408 in order to reduce the output level of, or otherwisemitigate, the interference in the signal output by the pair of antennaelements at the signal combiner 408. More particularly, as illustratedin FIG. 4 , a phase shifter or other component 410(1)-410(m-1) may beconfigured to apply a complex weight (e.g., with a real and an imaginarycomponent either of which may be zero) to the output from thetransmit/receive module 406 of one antenna element 404 of each pair ofantenna elements (e.g., to shift the amplitude and/or phase of theoutput signal) before it is combined with the output of thetransmit/receive module 406 of the other antenna element 404 of thepair.

In some implementations, a multi-channel receiver 412 may receive theinterference-mitigated signals output by signal combiners408(1)-408(m-1) (e.g., from signal couplers 411(1)-411(m-1) that tap theoutputs of signal combiners 408(1)-408(m-1)) and measure the power ineach such interference-mitigated signal. Based on feedback received fromthe multi-channel receiver 412 about the power level of each suchinterference-mitigated signal, a controller 414 may control the complexweights applied by components 410(1)-410(m-1) in an effort to minimizethe power measured in the interference-mitigated signals output by thesignal combiners 408(1)-408(m-1) in order to eliminate or reduce theinterference present in the interference-mitigated signals output bysignal combiners 408(1)-408(m-1).

As further illustrated in FIG. 4 , in some implementations, phaseshifters 416(1)-416(m-1) may apply complex weights (e.g., with real andimaginary components either of which may be zero) to, or otherwise shiftthe phase of, the corresponding outputs of signal combiners408(1)-408(m-1) which then are combined into a single,interference-mitigated output signal from the multielement antenna 402by signal combiner 418. The application of complex weights by phaseshifters 416(1)-416(m-1) to the outputs of signal combiners4081(1)-408(m-1) in this fashion may enable one or more main beams ofthe multielement antenna 402 to be steered in directions that arefavorable for transmitting and/or receiving signals.

The output of signal combiner 418 may be passed to a modem 420 foradditional processing. In addition, in some implementations, the modem420 may pass the output signal, or information about the output signal,to a controller 422 that controls the complex weights and/or phaseshifts applied by phase shifters 416(1)-416(m-1) to steer one or moremain beams of the multielement antenna 402 in directions that arefavorable for transmitting and/or receiving signals (e.g., based oncharacteristics of the output signal and/or a priori knowledge of thelocation of an intended transmitter of signals to be received by themultielement antenna 402). In some implementations, controllers 414 and422 may be implemented as separate and discrete components. Inalternative implementations, controllers 414 and 422 may be implementedas a single component. Additionally or alternatively, in someimplementations, the signals received by antenna elements 404(1)-404(m),output by transmit/receive modules 406(1)-406(m), received and output bysignal combiners 408(1)-408(m-1), and output by phase shifters416(1)-416(m-1) all may be RF signals.

Application of the teachings of the present disclosure may enable thesimultaneous operation of two or more wireless communication terminalslocated in close physical proximity to one another even if the wirelesscommunication terminals transmit and/or receive using similar, adjacent,neighboring, and/or overlapping frequencies. For example, application ofthe teachings of the present disclosure may enable an IRIDIUM® satellitecommunication terminal to be operated in the presence of a nearby activeINMARSAT® satellite communication terminal.

Aspects of the present disclosure may be implemented entirely inhardware, entirely in software (including firmware, resident software,micro-code, etc.) or in combinations of software and hardware that mayall generally be referred to herein as a “circuit,” “module,”“component,” or “system.” Furthermore, aspects of the present disclosuremay take the form of a computer program product embodied in one or morecomputer-readable media having computer-readable program code embodiedthereon.

Any combination of one or more computer-readable media may be utilized.The computer-readable media may be a computer-readable signal medium ora computer-readable storage medium. A computer-readable storage mediummay be, for example, but not limited to, an electronic, magnetic,optical, electromagnetic, or semiconductor system, apparatus, or device,or any suitable combination of the foregoing. More specific examples (anon-exhaustive list) of such a computer-readable storage medium includethe following: a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), an appropriate optical fiberwith a repeater, a portable compact disc read-only memory (CD-ROM), anoptical storage device, a magnetic storage device, or any suitablecombination of the foregoing. In the context of this document, acomputer-readable storage medium may be any tangible medium that cancontain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer-readable signal medium may include a propagated data signalwith computer-readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer-readable signal medium may be any computer-readable medium thatis not a computer-readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device. Program codeembodied on a computer-readable signal medium may be transmitted usingany appropriate medium, including but not limited to wireless, wireline,optical fiber cable, RF signals, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in any combination of one or moreprogramming languages, including object oriented programming languages,dynamic programming languages, and/or procedural programming languages.

The flowchart and block diagrams in the figures illustrate examples ofthe architecture, functionality, and operation of possibleimplementations of systems, methods and computer program productsaccording to various aspects of the present disclosure. In this regard,each block in the flowchart or block diagrams may represent a module,segment, or portion of code, which comprises one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that, in some alternative implementations, thefunctions noted in the block may occur out of the order illustrated inthe figures. For example, two blocks shown in succession may, in fact,be executed substantially concurrently, or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. It will also be noted that each block of the block diagramsand/or flowchart illustration, and combinations of blocks in the blockdiagrams and/or flowchart illustration, can be implemented by specialpurpose hardware-based systems that perform the specified functions oracts, or combinations of special purpose hardware and computerinstructions.

The interference mitigation techniques described herein may be employedin a wide variety of different contexts to enable concurrent operationof two or more co-located wireless communication terminals. For example,the interference mitigation techniques described herein may be employedto enable concurrent operation of two satellite communication terminalsmounted within a short distance of one another on a ship or aircraft.Similarly, the interference mitigation techniques described herein maybe employed to enable concurrent operation of two terminals (e.g.,transceivers) on a single satellite.

The terminology used herein is for the purpose of describing particularaspects only and is not intended to be limiting of the disclosure. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of anymeans or step plus function elements in the claims below are intended toinclude any disclosed structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of the present disclosure has been presentedfor purposes of illustration and description, but is not intended to beexhaustive or limited to the disclosure in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of thedisclosure. The aspects of the disclosure herein were chosen anddescribed in order to explain the principles of the disclosure and thepractical application, and to enable others of ordinary skill in the artto understand the disclosure with various modifications as are suited tothe particular use contemplated.

What is claimed is:
 1. A wireless, satellite communications terminal comprising: an antenna array having a plurality of m antenna elements arranged linearly and displaced from one another such that the displacement between each pair of adjacent antenna elements within the antenna array is substantially equal, wherein m is a number representing the plurality of antenna elements, and wherein each of the antenna elements include transmit/receive modules; a first plurality of m-1 phase shifters, wherein each phase shifter of the first plurality is coupled to a unique one of the antenna elements and is configured to receive, from the antenna element to which it is coupled, a signal received by the antenna element and to apply a complex weight to it to generate a complex-weighted version of the signal received by the antenna element; a plurality of m-1 first-stage signal combiners, wherein each first-stage signal combiner corresponds to a unique one of the pairs of adjacent antenna elements within the antenna array, is coupled to a first one of the pair of adjacent antenna elements and a phase shifter from the first plurality of phase shifters that is coupled to the second of the pair of adjacent antenna elements, and is configured to: receive, from the first of the pair of adjacent antenna elements, a signal received by the first antenna element, receive, from the phase shifter coupled to the second of the pair of adjacent antenna elements, the complex-weighted version of the signal received by the second antenna element, and combine the signal received by the first antenna element and the complex-weighted version of the signal received by the second antenna element to generate an output signal; a second plurality of m-1 phase shifters, wherein each phase shifter of the second plurality is coupled to a unique one of the first-stage signal combiners and is configured to receive, from the first-stage signal combiner to which it is coupled, the output signal output by the first-stage signal combiner and to apply a complex weight to it to generate a complex-weighted version of the output signal; a second-stage signal combiner coupled to each of the phase shifters of the second plurality and configured to combine the complex-weighted versions of the output signals output by the phase shifters of the second plurality to generate an interference-mitigated output signal for the antenna array; a first controller to set the complex weights applied by the first plurality of phase shifters to the signals received by the antenna elements to which they are connected to generate complex-weighted versions of the signals received by the antenna elements to which they are connected that model interference from a co-located wireless communication terminal; a second controller to set the complex weights applied by the second plurality of phase shifters to steer a main beam of the antenna array to facilitate reception of a desired signal; and wherein the signals received by the antenna elements, the complex-weighted versions of the signals received by the antenna elements, the output signals generated by the first-stage signal combiners, the complex-weighted versions of the output signals, and the interference-mitigated output signal for the antenna array all are RF signals.
 2. The wireless communications terminal of claim 1, wherein: phase shifters of the first plurality of phase shifters are configured to apply complex weights to the signals they receive from the antenna elements to which they are coupled by applying complex weights that have both real and imaginary parts; and phase shifters of the second plurality of phase shifters are configured to apply complex weights to the signals they receive from the first-stage signal combiners to which they are coupled by applying complex weights that have both real and imaginary parts.
 3. The wireless communications terminal of claim 2, wherein: the phase shifters of the first plurality of phase shifters that are configured to apply complex weights to the signals they receive from the antenna elements to which they are coupled are configured to apply complex weights that can have real parts that are zero and imaginary parts that are zero; and the phase shifters of the second plurality of phase shifters that are configured to apply complex weights to the signals they receive from the first-stage signal combiners to which they are coupled are configured to apply complex weights that can have real parts that are zero and imaginary parts that are zero.
 4. The wireless communications terminal of claim 1, wherein the antenna array is configured to transmit signals in addition to receiving signals and individual antenna elements are configured to transmit signals in addition to receiving signals.
 5. The wireless communications terminal of claim 1, further comprising: a multi-channel receiver configured to measure the power of the signals carried on its multiple channels and to transmit an output signal for the first controller that is indicative of the power of the signals measured by the multi-channel receiver; and a plurality of m-1 signal couplers, each signal coupler configured to couple the signal output by a unique one of the m-1 first-stage signal combiners to a corresponding unique channel of the multi-channel receiver, wherein: the first controller is configured to set the complex weights applied by the first plurality of phase shifters to minimize the power of the signals measured by the multi-channel receiver.
 6. The wireless communications terminal of claim 1, wherein the first and second controllers are implemented as distinct controllers.
 7. The wireless communications terminal of claim 1, wherein the first and second controllers are implemented as a single controller.
 8. The wireless communications terminal of claim 1, wherein the second controller is configured to set the complex weights applied by the second plurality of phase shifters to steer the main beam of the antenna array to facilitate reception of a desired signal from a satellite.
 9. A method for processing a desired signal by a wireless, satellite communication terminal, comprising: receiving signals with an antenna array having a plurality of m antenna elements arranged linearly and displaced from one another such that the displacement between each pair of adjacent antenna elements within the antenna array is substantially equal, wherein m is a number representing the plurality of antenna elements, and wherein each of the antenna elements include transmit/receive modules; accessing a first set of complex weights to be applied to the signals received by m-1 of the antenna elements; applying the first set of complex weights to the signals received by the m-1 antenna elements to generate complex-weighted versions of the corresponding signals received by the m-1 antenna elements; for each pair of adjacent antenna elements within the antenna array, combining the signal received by a first one of the pair of adjacent antenna elements with the complex-weighted version of the signal received by the second one of the pair of adjacent antenna elements to generate m-1 output signals; accessing a second set of complex weights to apply to the output signals; applying the second set of complex weights to the output signals to generate complex-weighted versions of the output signals; combining the complex-weighted versions of the output signals to generate an interference-mitigated output signal; and wherein the signals received by the antenna elements, the complex-weighted versions of the signals received by the antenna elements, the output signals generated by the first-stage signal combiners, the complex-weighted versions of the output signals, and the interference-mitigated output signal for the antenna array all are RF signals.
 10. The method of claim 9, wherein accessing a first set of complex weights to be applied to the signals received by m-1 of the antenna elements comprises setting a first set of complex weights to be applied to the signals received by m-1 of the antenna elements to minimize the power in the m-1 output signals generated by combining, for each pair of adjacent antenna elements within the antenna array, the signal received by a first one of the pair of adjacent antenna elements with the complex-weighted version of the signal received by the second one of the pair of adjacent antenna elements.
 11. The method of claim 9, wherein accessing a second set of complex weights comprises setting a second set of complex weights to steer a main beam of the antenna array to facilitate reception of a desired signal.
 12. The method of claim 11, wherein setting the second set of complex weights to steer the main beam of the antenna array to facilitate reception of a desired signal comprises setting the second set of complex weights to steer the main beam of the antenna array to facilitate reception of a desired signal from a satellite.
 13. A wireless, satellite communications terminal comprising: a multi-element antenna having a plurality of antenna elements, wherein each of the antenna elements include transmit/receive modules; a plurality of preliminary signal combiners, each preliminary signal combiner configured to combine received signals output by a corresponding pair of two antenna elements, wherein: the signal output by a first one of the pair of antenna elements provides a model of interference present in the received signal output by the second one of the pair of antenna elements, and the preliminary signal combiner is configured to combine the signal output by the first antenna element with the signal output by the second antenna element to produce an initial interference-mitigated signal; a plurality of phase shifters configured to apply complex weights to corresponding interference-mitigated signals to produce complex-weighted versions of the corresponding interference-mitigated signals and effectively steer a main beam of the multi-element antenna to facilitate reception of a desired signal; another signal combiner configured to combine the complex-weighted versions of the interference-mitigated signals to produce an interference-mitigated output signal; and a controller to set the complex weights applied by the plurality of phase shifters to steer the main beam of the multi-element antenna array to facilitate reception of the desired signal.
 14. The wireless communications terminal of claim 1, wherein the controller is configured to set the complex weights to facilitate reception of the desired signal from a satellite.
 15. The wireless communications terminal of claim 13, wherein: the multi-element antenna having a plurality of antenna elements comprises a multi-element antenna array having a plurality of antenna elements arranged linearly; and the plurality of preliminary signals combiners are configured to combine received signals output by pairs of adjacent antenna elements within the antenna array. 